The international permissible limit for PM2.5 is 25 micro grammes per cubic metre while for India, it is 60.

Air pollution intensified in the National Capital and the adjoining cities on Friday, with forecasts warning further worsening of situation in the next 24 hours and warning the very young or old and those with breathing problems to take precautions.

The average PM2.5 (particles in air with diameter less than 2.5 mm) level in Delhi till 8 p.m. was recorded at 119, considered 'poor', showed data by System of Air Quality and Weather Forecasting and Research (SAFAR).

The international permissible limit for PM2.5 is 25 micro grammes per cubic metre while for India, it is 60.

Cautioning, especially those with heart or lung diseases, apart from old people and children to avoid any prolonged or heavy exertion, SAFAR had forecast further intensification in PM2.5 levels in air on Saturday -- considered 'very poor'

"Everyone else should reduce prolonged or heavy exertion," said a health advisory by SAFAR, while it further elaborated 'health risk' as "everyone may experience more or serious health effects. Significant increase in respiratory effects in general population".

The assessments are based on the level of PM2.5, one of the major and common pollutants with direct consequences on life expectancy.

On Friday, the PM2.5 situation by 8.00 p.m. had crossed red-mark considered 'very poor' at five areas of Delhi, including Pitampura and Delhi University in the north, Lodhi Road, Mathura Road and Aya Nagar in the south.

According to the Delhi Pollution Control Committee (DPCC) data recorded at 8 p.m., the level of PM2.5 at Anand Vihar in east Delhi was 145, at Mandir Marg in central Delhi was 83, at Punjabi Bagh in west Delhi was 68 and R.K Puram in south Delhi was 171.

According to the Central Pollution Control Board (CPCB), the Air Quality Index (AQI) on Friday also showed a grim picture with Delhi's AQI further deteriorating in the past 24 hours and placed as 'poor' with index value 285.

On Thursday, Delhi's air quality, still poor, had an index value of 268.

Meanwhile, in neighbouring Ghaziabad in Uttar Pradesh, the situation seemed alarming, with air quality consistently falling for three days and fixed at the index value of 342 on Friday, which was 338 on Thursday and 296 on Wednesday.

In Haryana, Gurugram saw a moderate air quality while in Faridabad, the air quality was recorded as poor with index value 252.